Process for production of the maleic anhydride adduct of a liquid polymer

ABSTRACT

A process for production of the maleic anhydride adduct of a liquid polymer having a maleic anhydride addition amount of 2 to 70% by weight, which comprises reacting a liquid polymer having a molecular weight of 150 to 5,000 and a viscosity of 2 to 50,000 cp at 30° C in the presence of at least one compound, as a gelation inhibitor, selected from the group consisting of imidazoles, thiazoles, metallic salts of mercaptothiazoles, urea derivatives, naphthylamines, nitrosamines, iron, iron compounds and specific halogen compounds, said liquid polymer being selected from the group consisting of liquid polybutadienes, liquid polyisoprenes and liquid copolymers comprising units of butadiene or isoprene and units of at least one compound selected from the group consisting of other diolefins, olefins and aromatic vinyl compounds.

The present invention relates to a process for production of the maleic anhydride adduct of a liquid polymer having a maleic anhydride addition amount of 2 to 70% by weight.

Hitherto, it is well known to prepare the important materials for paints by reacting natural unsaturated oils such as soybean oil, linseed oil or castor oil with maleic anhydride. Many attempts have been made to use substitutes for the natural unsaturated oils in production of the said materials. For example, Japanese Patent Publication No. 21193/1961 discloses the production of the materials for alkyd resins by reacting cyclododecatriene with maleic anhydride. Japanese Patent Publication No. 954/1971 discloses the production of a modified polymer by the addition reaction of maleic anhydride to give low molecular weight polybutadiene having the 1,2-structure in an amount of not less than 80%. Japanese Patent Publication No. 7269/1971 discloses a method for the preparation of a water-soluble resin by neutralizing the said modified polymer or its esterified product with ammonia or an amine.

In the reaction wherein maleic anhydride adds to the polymers resulting from conjugated diolefins, the adducts are generally prepared by heating and, in this reaction, there is usually observed a tendency that, while the addition reaction proceeds, the double bonds of the polymers are crosslinked with other molecules according to the radical addition, whereby the viscosity of the reaction mass increases. When the viscosity is further increased, the reaction mass in the reaction vessel completely forms a gel to make the after-treatment very troublesome. Even if the gel is not formed, the increase of the viscosity in the maleinization causes various difficulties. For instance, the paints prepared by the use of the resulting maleinized products form a coating film having inferior physical properties. Further, for instance, the controls of the conversion of maleic anhydride and of the viscosity of the reaction mass for obtainment of the maleinized products having a suitable viscosity for paints are quite difficult.

Various trials have been made to overcome the said difficulties. For example, Japanese Patent Publication No. 3547/1973 proposes to use cyclic ethers, aldehydes or ketones as a gelation inhibitor in the maleinization reaction. Further, as such gelation inhibitor, there are proposed the uses of amides (Japanese Patent Publication No. 3544/1973), catechols (Japanese Patent Publication (unexamined) No. 7895/1975), naphthols (Japanese Patent Publication (unexamined) No. 87491/1975), phenothiazines (Japanese Patent Publication (unexamined) No. 132013/1974), etc.

On the other hand, Japanese Patent Publication No. 26870/1968 discloses the preparation of maleinized products by heating a liquid polybutadiene having the cis-1,4 structure in an amount of not less than 50% and a viscosity of 30 to 30,000 cp (centipoise), particularly 80 to 10,000 cp, at 50° C with maleic anhydride in the presence of a copper compound. This method is characterized in that the viscosity in maleinization is reduced by the existence of the copper compound. Further, Japanese Patent Publication No. 44557/1972 proposes the use of a complex-forming agent such as acetylacetone in such a reaction.

As the result of an extensive study seeking a gelation inhibitor which exerts a sufficient effect for preventing the formation of gels in the addition reaction of maleic anhydride to give conjugated diene polymers even when employed in a small amount, it has been found that imidazoles, thiazoles, metal salts of mercaptothiazoles, urea derivatives, naphthylamines, nitrosamines, iron and its compounds, and specific halogen compounds have such an effect and are utilizable as the gelation inhibitor.

The present invention is based on the above finding and provides a process for production of the maleic anhydride adduct of a liquid polymer having a molecular weight of 150 to 5,000 and a viscosity of 2 to 50,000 cps at 30° C in the presence of at least one compound, as a gelation inhibitor, selected from the group consisting of imidazoles, thiazoles, metal salts of mercaptothiazoles, urea derivatives, naphthylamines, nitrosamines, iron and its compounds and specific hydrogen compounds, said liquid polymer being selected from the group consisting of liquid polybutadienes, liquid polyisoprenes and liquid copolymers comprising units of butadiene or isoprene and units of at least one compound selected from the group consisting of other diolefins, olefins and aromatic vinyl compounds.

Compared with the said gelation inhibitors as disclosed in Japanese Patent Publication Nos. 26870/1968 and 44557/1972, the gelation inhibitors used in the present invention have various advantages. For instance, the gelation inhibitors of this invention can reduce sufficiently and satisfactorily the viscosity of the reaction mass by the use of a smaller amount than that of the known gelation inhibitors. This is advantageous in production of resinous materials to be used for paints since the influence by the gelation inhibitor can be suppressed. Further, for instance, the coloration of the maleinized product caused by the gelation inhibitors of the invention is much less than that caused by the known gelation inhibitors. This apparently contributes to the production of resinous materials of higher quality.

The working mechanism of the gelation inhibitors according to the present invention is still unclear. However, it is presently assumed that they are effective in decomposition and elimination of such radicals as hydroperoxy groups, oxy radicals and polymer radicals present in the molecules of the liquid polymer and/or molecular oxygen existing in the liquid polymer.

As the liquid polymer, there are utilizable liquid polybutadienes, liquid polyisoprenes, liquid butadiene copolymers and liquid isoprene copolymers, which may have a molecular weight of 150 to 5,000 and a viscosity of 2 to 50,000 cp at 30° C, irrespective of the proportion of the cis-, trans-, vinyl- and 3,4-structures constituting the micro structure of the liquid polymer. In case of the liquid polymer being a low molecular weight copolymer of butadiene or isoprene with styrene, it may contain styrene units in a proportion of not more than 40% by weight. The said liquid polymer can be prepared in a conventional procedure, for instance, as disclosed in U.S. Pat. No. 3,428,699.

The addition reaction of maleic anhydride to the liquid polymer in the presence of the gelation inhibitor may be carried out by charging the liquid polymer, maleic anhydride and the gelation inhibitor into a reaction vessel in an optional order and then heating at an elevated temperature until the maleinization is completed. Practically, for instance, the liquid polymer and the gelation inhibitor are first charged into a reaction vessel and kept at a temperature of 10° to 270° C for a period of 0 to 20 hours. Then maleic anhydride is added thereto, and the resultant mixture is heated at a temperature of 120° to 230° C, preferably of 170° to 210° C, for a period of 1 to 10 hours in a nitrogen stream under stirring. Alternatively, the liquid polymer, maleic anhydride and the gelation inhibitor may be charged in a reaction vessel from the beginning and then heated at a temperature of 120° to 230° C, preferably of 160° to 190° C, for a period of 1 to 10 hours in a nitrogen stream under stirring. Since the maleinization proceeds almost quantitatively, the recovery of unreacted materials from the reaction mixture is normally unnecessary. The content of the added maleic moiety in the maleinized product may be usually from 2 to 70% by weight. When the maleinized product is blended with an inorganic pigment to prepare a paint composition, the maleic anhydride content is particularly desired to be not less than 2% by weight.

As the gelation inhibitor used in the present invention, there may be exemplified the following compounds:

(1) Imidazoles of the formulae: ##STR1## wherein R₁, R₂ and R₃ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a halogen atom and X is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, a mercapto group or a halogen atom. Specific examples are imidazole, 4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 2,4-dimethylimidazole, 4,5-dimethylimidazole, 2,4-diphenylimidazole, 4,5-diphenylimidazole, 2,4,5-triphenylimidazole, 2-bromo-4-methylimidazole, 2-bromo-4-phenylimidazole, 4-bromo-1-methylimidazole, 2,4-dibromoimidazole, 2,4,5-tribromoimidazole, 2,4,5-triiodoimidazole, 2-mercaptoimidazole, 2-mercapto-4-methylimidazole, 2-mercapto-4,5-dimethylimidazole, 2-mercapto-4-phenylimidazole, benzimidazole, 2-methylbenzimidazole, 2-ethylbenzimidazole, 2-vinylbenzimidazole, 2-phenylbenzimidazole, 2-benzylbenzimidazole, 5-methylbenzimidazole, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, etc. Among these imidazoles, mercaptoimidazoles and benzimidazoles are preferred.

2. Thiazoles of the formulae: ##STR2## wherein R₄, R₅ and R₆ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a halogen atom or a phenyl group and X' is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, a halogen atom, a mercapto group, a hydroxyl group of a hydroxymethyl group, or a group of the formula: --SNR₇ R₈ in which R₇ and R₈ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alicyclic group. Specific examples are 2-methylthiazole, 4-methylthiazole, 5-methylthiazole, 2,4-dimethylthiazole, 2,5-dimethylthiazole, 4,5-dimethyltiazole, 2,4,5-trimethylthiazole, 2-ethylthiazole, 2-phenylthiazole, 4-phenylthiazole, 5-phenylthiazole, 2-methyl-4-phenylthiazole, 4-methyl-5-phenylthiazole, 4,5-diphenylthiazole, 2-methyl-4,5-diphenylthiazole, 2-methylcyclohexenothiazole, 2-mercaptocyclohexenothiazole, 2-chlorothiazole, 2-bromothiazole, 2-chloro-4-methylthiazole, 4-chloromethylthiazole, 4-chloromethyl-2-methylthiazole, 4-chloromethyl-2-phenylthiazole, 2-hydroxy-4-methylthiazole, 2-methoxy-4-methylthiazole, 2-hydroxy-5-methylthiazole, 2-hydroxy-4,5-diphenylthiazole, 2-hydroxymethyl-4-methylthiazole, 2-aminothiazole, 2-amino-4,5-diphenylthiazole, 2-amino-5-phenylthiazole, benzthiazole, 2-ethylbenzthiazole, 2-methylbenzthiazole, 2-phenylbenzthiazole, 2-chlorobenzthiazole, 2-hydroxybenzthiazole, 2-hydroxy-5-methylbenzthiazole, 2-aminobenzthiazole, 2-amino-6-methylbenzthiazole, 2mercaptobenzthiazole, etc. When X is a group represented by the formula: --SNR₇ R₈, the thiazoles are generally called "thiazylsulfenamides", and their examples include N-ethylthiazylsulfenamide, N-propylthiazylsulfenamide, N-butylthiazylsulfenamide, N-amylthiazylsulfenamide, N-octylthiazylsulfenamide, N-cyclohexylthiazylsulfenamide, N-oxydiethylenethiazylsulfenamide, N-ethylbenzthiazylsulfenamide, N-propylbenzthiazylsulfenamide, N-butylbenzthiazylsulfenamide, N-octylbenzthiazylsulfenamide, N-cyclohexylbenzthiazylsulfenamide, N-oxydiethylenebenzthiazylsulfenamide and the like. Among the foregoing thiazoles, benzthiazoles are particularly preferred.

3. Metal salts of mercaptothiazoles of the formula: ##STR3## wherein R₉, R₁₀ and R₁₁ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a halogen atom or a phenyl group and M is zinc, aluminum, magnesium or calcium. Specific examples include zinc salts, calcium salts, magnesium salts and aluminum salts of 2-mercaptothiazole, 2-mercapto-4-methylthiazole, 2-mercapto-5-methylthiazole, 2-mercapto-4,5-dimethylthiazole, 2-mercapto-4-ethylthiazole, 2-mercapto-4-chlorothiazole, 2-mercapto-4-phenylthiazole, 2-mercapto-4-methyl-5-phenylthiazole, 2-mercaptocyclohexenothiazole, 2-mercaptobenzthiazole and the like. Among these salts, matal salts of benzthiazoles are particularly preferred.

4. Urea derivatives of the formula: ##STR4## wherein R₁₂ and R₁₃ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a phenyl group and X" is an imino group or a sulfur atom. Specific examples include guanidine, diphenylguanidine, dimethylguanidine, diphenylthiourea and the like. The inorganic or organic salts (e.g. hydrochlorides, sulfates, carbonates, acetates, oxalates) of the foregoing compounds as well as the adducts of the foregoing compounds with acetic anhydride, phthalic anhydride, maleic anhydride, etc. are also utilizable.

5. Naphthylamines

As the naphthylamines, α-naphthylamine, β-naphthylamine, N-phenyl-α-naphthylamine, N-phenyl-β-naphthylamine and N,N'-di-β-naphthyl-p-phenylenediamine are preferred.

6. Nitrosamines of the formula: ##STR5## wherein R₁₄ and R₁₅ are each an alkyl group having 1 to 8 carbon atoms or a phenyl group. Preferred compounds are dimethylnitrosamine, diethylnitrosamine, dipropylnitrosamine, dibutylnitrosamine, dioctylnitrosamine, didodecylnitrosamine, diphenylnitrosamine, ditolylnitrosamine, dicyclohexylnitrosamine, etc.

7. Iron and its compounds

Among iron and its compounds, preferred are those soluble in organic solvents. However, even the insoluble compounds have an antigelling effect. As the organic salts of iron, there may be exemplified the iron salts of organic carboxylic acids such as iron acetate, iron naphthenate, iron octylate and iron benzoate. As the organic complexes of iron, there may be exemplified the complex between iron chloride and pyridine, tris-(dipyridyl)iron chloride, bis(ethylenediamine)iron sulfate and the like. The chelate compounds of iron such as bis-(acetylacetonate)iron, bis-(ethylacetoacetate)iron and bis-(dimethylglyoximate)iron may be also employed. Further, inorganic iron compounds such as iron sulfate, iron nitrate, iron oxide, ferrous chloride, ferric chloride, ferrous bromide, ferric bromide, iron iodide and iron powder are utilizable.

8. Halogen-containing compounds

A. Elements belonging to Group (III), (IV), (V) or (VI) in the Periodic Table are used in the form of chlorides, bromides or iodides, or ether complexes, ester complexes or aldehyde complexes thereof. As the elements, there may be exemplified phosphorus, boron, aluminum, gallium, indium, thallium, titanium, germanium, zirconium, tin, vanadium, arsenic, antimony, tantalum, bismuth, chromium, molybdenum and the like. Specific examples include boron trichloride, aluminum trichloride, gallium trichloride, indium trichloride, titanium tetrachloride, zirconium tetrachloride, tin chloride, antimony trichloride, antimony pentachloride, phosphorus trichloride, tungsten hexachloride, molybdenum tetrachloride, phosphorus pentachloride, phosphorus tribromide, phosphorus pentabromide, arsenic trichloride, arsenic tribromide, antimony tribromide, antimony triiodide, antimony pentabromide, boron tribromide, boron triiodide, aluminum tribromide, titanium tetrabromide, titanium tetraiodide and the like, and ether complexes, ester complexes and aldehyde complexes of the foregoing compounds.

B. Hydrogen halogenides represented by the formula: HX'" wherein X'" is a chlorine, bromine or iodine atom are used. Specific examples include hydrogen chloride, hydrogen bromide and hydrogen iodide.

C. Alkyl metal halides represented by the formula:

    R.sub.n M'Y.sub.m-n

wherein M' is a metal belonging to Group (III) or (IV) of the Periodic Table, R is an alkyl group, Y is a chlorine atom, a bromine atom or an iodine atom, m is a valence of the metal (M') and n is a positive integer smaller than m are used. Specific examples include dimethylaluminum chloride, diethylaluminum chloride, diisobutylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, diethylaluminum bromide, diethylaluminum iodide, dimethylboron monochloride, diethylboron monochloride, dibutylboron monochloride, methylboron dichloride, ethylboron dichloride, butylboron dichloride, boron trichloride, dimethylboron monobromide, diethylboron monobromide, dibutylboron monobromide, diphenylboron monobromide, methylboron dibromide, ethylboron dibromide, propylboron dibromide, butylboron dibromide, boron tribromide, dimethylboron monoiodide, diethylboron monoiodide, dipropylboron monoiodide, dibutylboron monoiodide, diphenylboron monoiodide, methylboron diiodide, ethylboron diiodide, butylboron diiodide, boron triiodide, methyltin trichloride, dimethyltin dichloride, ethyltin trichloride, butyltin trichloride, diphenyltin dichloride, trimethyltin bromide and trimethyltin iodide.

D. Halogenated compounds of aliphatic or alicyclic hydrocarbons having 1 to 8 carbon atoms are used. Specific examples include carbon tetrachloride, chloroform, bromoform, iodoform, dichloroethane, bromochloromethane, dibromoethane, diiodomethane, ethyl bromide, ethyl chloride, isobutyl chloride, isobutyl bromide, n-butyl bromide, tert-butyl bromide, tert-butyl chloride, 2-iodopropane, 2-bromodecane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, pentachloroethane, hexachloroethane, hexachlorocyclopentadiene, 5-chloronorbornane, 5-chloromethylnorbornane, 5-bromonorbornane, 5-bromomethylnorbornane, etc.

E. Compounds of the formula: ##STR6## wherein R₁₆ is a chlorine atom, a bromine atom or an iodine atom, R₁₇ and R₁₈ are each a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, a lower alkyl or a phenyl group and R₁₉ and R₂₀ are each a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms or a halogen substituted alkyl group are used. Specific examples include benzyl chloride, benzyl bromide, benzyl iodide, α-methylbenzyl bromide, α-methylbenzyl chloride, triphenylmethyl chloride, triphenylmethyl bromide, benzotrichloride, 2,4-dichlorobenzotrichloride, benzotribromide, α,2,4-trichlorotoluene, α,3,4-trichlorotoluene, m-xylylene chloride, m-xylylene bromide, o-xylylene bromide, p-xylylene bromide, o-xylylene chloride, p-xylylene chloride, m-xylylene tetrabromide, o-xylylene tetrabromide, p-xylylene tetrabromide, α,α,α,α',α',α'-hexachloro-m-xylene, α,α,α,α',α',α'-hexachloro-o-xylene, benzal chloride, 2,6-dichlorobenzal chloride and and the like.

F. As the alkynyl halides, there may be exemplified propargyl chloride, propargyl bromide, etc.

G. Ketones containing a chlorine atom or a bromine atom are used. Specific examples include 1,3-dichloroacetone, 1,1,3,3-tetrachloroacetone, bromoacetone, 1,3-dibromoacetone, hexachloroacetone and the like.

H. Halogen-containing allyl compounds of the formula:

    R.sub.21 CH═CHCH.sub.2 Y'

wherein R₂₁ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 6 carbon atoms and Y' is a chlorine atom, a bromine atom or an iodine atom are used.

Among the gelation inhibitors described above, thiazoles, metal salts of mercaptothiazoles, naphthylamines, and iron and its compounds are especially preferred.

The gelatin inhibitor may be used in an amount of 0.001 to 5%, preferably 0.005 to 0.5%, based on the liquid polymer. The gelation inhibitor may be employed as such or in the form of a solution in an organic solvent.

The addition reaction of maleic anhydride to the liquid polymer is usually carried out without any solvents. However, organic solvents may be used, if necessary. Examples of such solvents are aliphatic hydrocarbons (e.g. liquid paraffin, n-paraffin, petroleum benzin), alicyclic hydrocarbons (e.g. cyclohexane, isopropylcyclohexane), aromatic hydrocarbons (e.g. benzene, toluene, xylene, durene), ester compounds (e.g. ethyl acetate, butyl acetate), etc. Other organic solvents such as acetone, methyl ethyl ketone and dioxane are also utilizable.

The maleic anhydride adducts obtained by the present invention can remarkably be accelerated in the air-drying rate by adding a conventional hardening agent such as cobalt naphthenate thereto. Further, polyols, polymercaptanes, polyamines, polyphenols and the like can be used for hardening the coating film.

Practical embodiments of the present invention are illustratively shown in the following examples, which are not however intended to limit the present invention thereto. In these examples, % are usually by weight unless otherwise indicated.

EXAMPLE 1

Into a 300 ml volume flask, 160 g of a liquid polybutadiene having the following physical properties were charged, and a designed amount of the gelatin inhibitor as shown in Table 1 was added thereto:

    ______________________________________                                         Viscosity (cp, 20° C)                                                                             660                                                  Specific gravity (d.sub.4.sup.20, g/ml)                                                                  0.904                                                Iodine value (iodine g/100 g)                                                                            450                                                  Molecular weight (measured by                                                                            1,730                                                a pressure osmometer)                                                          Structure (%)                                                                               cis-1,4 structure                                                                               75                                                            trans-1,4 structure                                                                             23                                                            vinyl structure  2                                                ______________________________________                                    

After replacing the air in the flask by nitrogen gas, the mixture was heated at 150° C for 1 hour with stirring. Then, 34 g of maleic anhydride were added thereto, and the maleinization reaction was carried out at 190° C for 5 hours, during which the reaction mixture was sampled at 3, 4 and 5 hours from the initiation of the reaction and subjected to quantitative measurements of the conversion of maleic anhydride by means of gas chromatography. After completion of the reaction, the produced maleinized polybutadiene was dissolved in xylene to make a solid content of 70% and measured for viscosity at 25° C by means of the E-type viscometer (manufactured by Tokyo Keiki Co., Ltd.).

The results are shown in Table 1 wherein the results from the maleinization reactions carried out with copper naphthenate as the gelation inhibitor or without any gelation inhibitor are also indicated for comparison.

From Table 1, it is apparent that the gelation inhibitors according to the present invention have a higher effect than copper naphthenate at the same amount used. It is also apparent that the gelation inhibitors according to the present invention do not cause any material reduction of the conversion of maleic anhydride.

                                      Table 1                                      __________________________________________________________________________                                  Viscosity                                         Gelation inhibitor           in solu-                                                                               Conversion of maleic                                           Amount used                                                                            tion    anhydride (%)                             Run No.                                                                              Name           (% by weight)                                                                          (cp, 25° C)                                                                     3 hrs.                                                                              4 hrs.                                                                              5 hrs.                          __________________________________________________________________________     1     2-Mercaptobenzthiazole                                                                        0.0300   820    98.8 99.1 99.9                            2     2-Mercaptobenzimidazole                                                                       0.0300   960    98.7 99.2 99.9                            3     Diphenylguanidine                                                                             0.0300  1050    98.9 99.1 99.9                            4     2-Mercaptoimidazole                                                                           0.0300   930    98.9 99.1 99.9                            5     2-Hydroxy-4-methylthiazole                                                                    0.0300  1530    98.6 99.2 99.9                            6     Diphenylthiourea                                                                              0.0300  1320    98.7 99.1 99.9                            Reference                                                                            None           --      4004    98.8 99.1 99.9                            No. 1                                                                          Reference                                                                            Copper naphthenate                                                                            0.0300  2960    98.7 99.1 99.9                            No. 2                                                                          __________________________________________________________________________

EXAMPLE 2

Into a 300 ml volume flask, 166 g of the liquid polybutadiene as in Example 1 were charged, and a designed amount of the gelation inhibitor as shown in Table 2 was added thereto. After replacing the air in the flask by nitrogen gas, the mixture was heated at 100° C for 1 hour. Then, 34 g of maleic anhydride were added thereto, and the maleinization reaction was carried out at 190° C for 5 hours. After completion of the reaction, the produced maleinized polybutadiene was dissolved in xylene to make a solid content of 75% and measured for viscosity at 25° C.

The results are shown in Table 2, from which it is apparent that the gelation inhibitors according to the present invention have an excellent effect.

                                      Table 2                                      __________________________________________________________________________     Gelation inhibitor              Viscosity                                                              Amount used                                                                            in solu-                                                                               Conversion of                                                  (ppm, based                                                                            tion    maleic anhyd-                          Run No.                                                                              Name              on polymer)                                                                            (cp, 25° C)                                                                     ride (%)                               __________________________________________________________________________     1     N-t-Butylbenzthiazylsulfenamide                                                                  100     750     99.9                                   2     N-Cyclohexylbenzthiazylsulfen-                                                                   100     830     99.9                                         amide                                                                    3     N-Hydroxydiethylenebenzthiazyl-                                                                  200     660     99.9                                         sulfenamide                                                              4     Zinc salt of 2-mercaptobenz-                                                                     100     600     99.9                                         thiazole                                                                 5     Guanidine hydrochloride                                                                          100     430     99.9                                   6     Diphenylguanidine hydrochloride                                                                  100     480     99.9                                   7     N-Nitrosodiphenylamine                                                                           100     630     99.9                                   Reference                                                                            None              --      6800    99.9                                   No. 1                                                                          Reference                                                                            Copper naphthenate                                                                               300     2600    99.9                                   No. 2                                                                          __________________________________________________________________________

EXAMPLE 3

The gelation inhibitors according to the present invention were tested for the antigelling effect on the addition reaction of maleic anhydride to a mixture of a liquid polybutadiene having a high content of the cis-1,4 structure and a liquid polybutadiene having a high content of the 1,2-structure. Said cis-1,4 type liquid polybutadiene used was the same one as in Example 1, and said 1,2-type liquid polybutadiene used was the one having a number average molecular weight of 1,000 and consisting of 92% of the 1,2-structure and 8% of the trans-1,4 structure (trade name "B-1000" manufactured by Nippon Soda Co., Ltd.).

To a 300 ml volume flask equipped with a stirrer were added 83 g of the cis-1,4 type polybutadiene and 83 g of the 1,2-type polybutadiene. After replacing the air in the flask by nitrogen gas, the mixture was heated. When the temperature reached 100° C, 28 g of maleic anhydride and the gelation inhibitor were added thereto, followed by reaction at 190° C for 5 hours. The conversion of maleic anhydride was quantitatively measured by means of gas chromatography. The viscosity of the resulting maleinized product was determined on the xylene solution having a solid content of 75%.

The results are shown in Table 3, from which it is apparent that the gelation inhibitors according to the present invention have a high effect.

                                      Table 3                                      __________________________________________________________________________     Gelation inhibitor              Viscosity                                                              Amount used                                                                            in solu-                                                                               Conversion of                                                  (ppm, based                                                                            tion    maleic anhyd-                          Run No.                                                                              Name              on polymer)                                                                            (cp, 25° C)                                                                     ride (%)                               __________________________________________________________________________     1     N-Phenyl-α-naphthylamine                                                                   200      930    99.9                                   2     Diphenylguanidine hydrochloride                                                                  200      850    99.9                                   3     Zinc salt of 2-mercaptobenz-                                                                     100     2300    99.9                                         thiazole                                                                 4     Guanidine carbonate                                                                              100     2080    99.9                                   5     N-Nitrosodiphenylamine                                                                           100     1900    99.9                                   6     N-Cyclohexylbenzthiazylsulfen-                                                                   100     1280    99.9                                         amide                                                                    Reference                                                                            None              --      reaction                                                                               --                                     No. 1                           mass gelled                                                                    after 2 hrs.                                                                   at 190° C;                                                              reaction                                                                       stopped                                        __________________________________________________________________________

EXAMPLE 4

Maleinization reaction was carried out under the same conditions as in Example 1 except that a different gelation inhibitor was used. The resulting maleinized polybutadiene was dissolved in xylene to make a solid content of 70% and subjected to measurement for viscosity at 25° C by means of the E-type viscometer.

The results are shown in Table 4 wherein the results from the maleinization reactions carried out with acetylacetone, copper naphthenate, hydroquinone or 2,6-ditert-butoxytoluene as the gelation inhibitor or without any gelation inhibitor are also indicated for comparison.

From Table 4, it is apparent that both hydroquinone and 2,6-di-tert-butoxytoluene exhibit little or no gelation inhibiting effect, while the gelation inhibitors according to the present invention can keep the viscosity fairly low.

                                      Table 4                                      __________________________________________________________________________     Gelation inhibitor                                                                               Amount                                                                         used  Viscosity in solution                                                                          Conversion of maleic                                     (% by (cp, 25° C)                                                                             anhydride (%)                          Run No.                                                                              Name        weight)                                                                              3 hrs.                                                                               4 hrs.                                                                              5 hrs.                                                                              3 hrs.                                                                             4 hrs.                                                                             5 hrs.                         __________________________________________________________________________     1     Hexachloroacetone                                                                          0.021 4639  6656 7475 99.2                                                                               99.9                                                                               99.9                           2     Benzotrichloride                                                                           0.037 1265  1715 2355 98.9                                                                               99.4                                                                               99.9                           3     Phosphorus tri-                                                                            0.021  904  1214 1344 97.5                                                                               99.8                                                                               99.9                                 chloride                                                                 4     Aluminum tri-                                                                              0.025  563  1170 1221 98.8                                                                               99.3                                                                               99.9                                 chloride                                                                 5     Titanium tetra-                                                                            0.027  963  1114 1142 98.9                                                                               99.3                                                                               99.9                                 chloride                                                                 Reference                                                                            None        --    increase                                                                             gela-                                                                               --   --  --  --                             No. 1                   in visco-                                                                            tion                                                                     sity                                                   Reference                                                                            Hydroquinone                                                                               0.415 15300 23000                                                                               gela-                                                                               98.9                                                                               99.5                                                                               99.9                           No. 2                         tion                                             Reference                                                                            2,6-Di-tert-butoxy-                                                                        0.500 increase                                                                             --   --   --  --  --                             No. 3 toluene           in visco-                                                                      sity                                                   Reference                                                                            Copper naphthenate                                                                         0.021 4350  6700 8630 98.6                                                                               99.1                                                                               99.9                           No. 4                                                                          Reference                                                                            Acetylacetone                                                                              0.100 21320 28750                                                                               36200                                                                               98.8                                                                               99.6                                                                               99.9                           No. 5                                                                          __________________________________________________________________________

EXAMPLE 5

To a 200 ml volume three-necked glass flask were charged the gelation inhibitor and 100 g of a liquid polybutadiene having the following physical properties:

    ______________________________________                                         Viscosity (cp, 30° C)                                                                             74                                                   Molecular weight (measured by                                                                            660                                                  a pressure osmometer)                                                          Specific gravity (d.sub.4.sup.20, g/ml)                                                                  0.872                                                Iodine value (Wijs method)                                                                               461                                                  Micro-structure (%)                                                                               cis-1,4 structure                                                                             65.1                                                            trans-1,4 structure                                                                           27.0                                                            vinyl structure                                                                               7.9                                          ______________________________________                                    

After replacing the air in the flask by nitrogen gas, the mixture was stirred vigorously at 150° C for 1 hour. Thereafter, a designed amount of maleic anhydride was added thereto, and maleinization was carried out at 190° C for 5 hours in a nitrogen stream. After completion of the reaction, the reaction product was sampled and tested for solubility in toluene.

The results are shown in Table 5 wherein the results from the maleinization reaction carried out without any gelation inhibitor are used indicated for comparison.

                                      Table 5                                      __________________________________________________________________________     Maleic anhydride  Gelation inhibitor       Conversion                                     Weight % in      Weight % in    of maleic                                 Amount                                                                              the reac-   Amount                                                                              reac-  Viscosity                                                                              anhydride                                                                            Solubility                    Run No.                                                                              (g)  tion mass                                                                             Kind (g)  tion mass                                                                             (cp, 25° C)                                                                     (%)   in toluene                    __________________________________________________________________________       1   20.5 17     Iron 0.48 0.40    860    99    Completely                                      naph-                          dissolved                                       thenate                                                      Reference                                                                            20.5 17     None --   --     2450    99    Completely                    No. 1                                            dissolved                     __________________________________________________________________________

EXAMPLE 6

Maleinization reaction was carried out under the same conditions as in Example 1 except that the liquid polybutadiene used had the following physical properties:

    ______________________________________                                         Viscosity (cp, 20° C)                                                                             800                                                  Specific gravity (d.sub.4.sup.20, g/ml)                                                                  0.898                                                Iodine value (iodine g/100 g)                                                                            450                                                  Molecular weight (measured by a                                                                          1,970                                                pressure osmometer)                                                            Micro-structure (%)                                                                               cis-1,4 structure                                                                             79                                                              trans-1,4 structure                                                                           19                                                              vinyl structure                                                                               2                                            ______________________________________                                    

During the maleinization reaction, samplings were carried out at 3, 4 and 5 hours from the initiation of the reaction, and the quantitative measurements of the conversion of maleic anhydride were carried out by means of gas chromatography. After completion of the reaction, the resulting maleinized polybutadiene was dissolved in xylene to make a solid content of 60 % and measured for viscosity at 25° C by means of the E-type viscometer.

The results are shown in Table 6 wherein the results from the maleinization reactions carried out with copper naphthenate as the gelation inhibitor or without any gelation inhibitor are also indicated for comparison. When the gelation inhibitor was not used, the reaction mass gelled 3 hours after the initiation of the reaction and adhered to the stirrer. After the gel was once formed, it was no longer soluble in xylene.

From Table 6, it is apparent that the gelation inhibitors according to the present invention have a higher viscosity reducing effect than copper naphthenate.

                                      Table 6                                      __________________________________________________________________________     Gelation inhibitor                                                                         Weight %                                                                       in the                                                                               Weight of                                                                maleini-                                                                             metal Viscosity in solu-                                                                         Conversion of maleic                                   zed   atom  tion (cp, 25° C)                                                                    anhydride (%)                              Run No.                                                                              Kind  product                                                                              (ppm)*.sup.1)                                                                        3 hrs.                                                                             4 hrs.                                                                             5 hrs.                                                                             3 hrs.                                                                             4 hrs.                                                                             5 hrs.                             __________________________________________________________________________      1    Iron naph-                                                                     thenate                                                                              0.363 306   614 888 1050                                                                               97.3                                                                               99.0                                                                               99.9                                2    Iron naph-                                                                     thenate                                                                              0.073  61   --  --  --  96.7                                                                               99.2                                                                               99.9                                3    Ferric                                                                         chloride*.sup.2)                                                                      0.0253                                                                               35   367 418  481                                                                               98.1                                                                               99.9                                                                               99.9                               Reference                                                                            None  --    --    gela-                                                                              --  --  --  --  --                                 No. 1                   tion                                                   Reference                                                                            Copper                                                                   No. 2 naphthe-                                                                       nate  0.421 306   804 1229                                                                               1423                                                                               97.6                                                                               99.3                                                                               99.9                               Reference                                                                            Hydroqui-                                                                            0.421 --    gela-                                                                              --  --  --  --  --                                 No. 3 none              tion                                                   __________________________________________________________________________      Note:                                                                          *.sup.1) The weight of the metal atom is indicated by the amount of the        metal compound in the liquid polybutadiene in terms of the metal atom          (ppm).                                                                         *.sup.2) The ferric chloride means anhydrous ferric chloride, and it was       dissolved in methyl ethyl ketone to make a concentration of 0.05 g/ml and      used for the reaction.                                                   

EXAMPLE 7

Thirty grams of a liquid polyisoprene having the following physical properties, 7.5 g of maleic anhydride and a designed amount of the gelation inhibitor were charged in a flask:

    ______________________________________                                         Molecular weight          450                                                  Viscosity (cp, 30° C)                                                                             110                                                  Iodine value              400                                                  Micro-structure (%)                                                                               cis-1,4 structure                                                                             34                                                              trans-1,4 structure                                                                           41                                                              3,4-structure  24.0                                                            1,2-structure  1.0                                          ______________________________________                                    

After replacing the air by nitrogen gas, the mixture was heated at 190° C for 5 hours with stirring. Thereafter, the resulting maleinized polyisoprene was diluted with xylene to make a solid content of 75%, and the resulting solution was measured for viscosity at 25° C by means of the E-type viscometer.

The results are shown in Table 7.

                                      Table 7                                      __________________________________________________________________________     Gelation inhibitor                                                                           Amount used         Conversion of                                              on the poly-                                                                          Viscosity in solution                                                                       maleic anhydride                             Run No.                                                                              Name    mer)   (cp, 25° C)                                                                          (%)                                          __________________________________________________________________________      1    N-Phenyl-α-                                                                      200    480          99.9                                               naphthylamine                                                            Reference                                                                      No. 1 None    --     940          99.9                                         __________________________________________________________________________

EXAMPLE 8

Fifteen grams of the liquid polyisoprene as in Example 7, 15 g of a liquid polybutadiene having a high content of the 1,2-structure (i.e. the one having a number average molecular weight of 1,000 and consisting of 92% of the 1,2-structure and 8% of the trans-1,4 structure), 7.5 g of maleic anhydride and a designed amount of the gelation inhibitor were charged in a flask. After replacing the air by nitrogen gas, the mixture was heated at 190° C for 5 hours with stirring. The resulting maleinized product was diluted with xylene to make a solid content of 75%, and the resultant xylene solution was measured for viscosity at 25° C by means of the E-type viscometer.

The results are shown in Table 8.

                                      Table 8                                      __________________________________________________________________________     Gelation inhibitor                                                                           Amount used         Conversion of                                              on the poly-                                                                          Viscosity in solution                                                                       maleic anhydride                             Run No.                                                                              Name    mer)   (cp, 25° C)                                                                          (%)                                          __________________________________________________________________________      1    N-Phenyl-α-                                                                      200    1080         99.9                                               naphthylamine                                                            Reference                                                                      No. 1 None    --     1800         99.9                                         __________________________________________________________________________ 

What is claimed is:
 1. A process for production of the maleic anhydride adducts of a liquid polymer having a maleic anhydride addition amount of 2 to 70% by weight, which comprises reacting a liquid polymer having a molecular weight of 150 to 5,000 and a viscosity of 2 to 50,000 centipoise at 30° C, said liquid polymer being selected from the group consisting of liquid polybutadienes, liquid polyisoprenes and liquid copolymers comprising units of butadiene or isoprene and units of at least one compound selected from the group consisting of other diolefins, olefins and aromatic vinyl compounds, with maleic anhydride in the presence of at least one compound, as a gelation inhibitor, selected from the group consisting of:
 1. imidazoles of the formula: ##STR7## wherein R₁, R₂ and R₃ are each hydrogen, alkyl having 1 to 8 carbon atoms or halogen and mercapto
 2. 2. thiazoles of the formula: ##STR8## wherein R₄, R₅ and R₆ are each hydrogen, alkyl having 1 to 8 carbon atoms, halogen or phenyl and X' is hydrogen, alkyl having 1 to 8 carbon atoms, phenyl, halogen, mercapto, hydroxyl or hydroxymethyl, or a group of the formula: -SNR₇ R₈, in which R₇ and R₈ are each hydrogen, alkyl having 1 to 8 carbon atom or an alicyclic group;
 3. 3. metal salts of mercaptothiazoles of the formula: ##STR9## wherein R₉, R₁₀ and R₁₁ are each hydrogen, alkyl having 1 to 8 carbon atoms, halogen or phenyl and M is zinc, aluminum, magnesium or calcium;
 4. 4. urea derivatives of the formula: ##STR10## wherein R₁₂ and R₁₃ are each hydrogen, alkyl having 1 to 8 carbon atoms or phenyl and sulfur, and inorganic or organic acid salts thereof and acid anhydride adducts thereof.
 2. A method according to claim 1, wherein the gelation inhibitor is an imidazole compound selected from the group consisting of 2-mercaptoimidazole, 2-mercapto-4-methylimidazole, 2-mercapto-4,5-dimethylimidazole, 2-mercapto-4-phenylimidazole, 2-mercaptobenzimidazole and 2-mercapto-5-methylbenzimidazole.
 3. A method according to claim 1, wherein the gelation inhibitor is a thiazole compound selected from the group consisting of benzthiazole, 2-ethylbenzthiazole, 2-methylbenzthiazole, 2-phenylbenzthiazole, 2-chlorobenzthiazole, 2-hydroxybenzthiazole, 2-hydroxy-5-methylbenzthiazole, 2-aminobenzthiazole, 2-amino-6-methylbenzthiazole, 2-mercaptobenzthiazole, N-ethylbenzthiazylsulfenamide, N-propylbenzthiazylsulfenamide, N-butylbenzthiazylsulfenamide, N-octylbenzthiazylsulfenamide, N-cyclohexylbenzthiazylsulfenamide and N-oxydiethylenebenzthiazylsulfenamide.
 4. A method according to claim 1, wherein the gelation inhibitor is diphenylthiorurea, or a hydrochloride, sulfate, carbonate, acetate or oxalate thereof, or an acetic anhydride, phthalic anhydride or maleic anhydride adduct thereof.
 5. A process for the production of the maleic anhydride adducts of a liquid polymer having a maleic anhydride addition amount of 2 to 70% by weight, which comprises reacting a liquid polymer having a molecular weight of 150 to 5,000 and a viscosity of 2 to 50,000 centipoise at 30° C., said liquid polymer being selected from the group consisting of liquid polybutadienes, liquid polyisoprenes and liquid copolymers comprising units of butadiene or isoprene and units of at least one compound selected from the group consisting of other diolefins, olefins and aromatic vinyl compounds, with maleic anhydride in the presence of at least one compound, as a gelation inhibitor, selected from the group consisting of metal salts of mercaptothiazoles of the formula: or a hydrochloride, sulfate, carbonate, acetate or oxalate thereof, or an acetic anhydride, phthalic anhydride or maleic anhydride adduct thereof. ##STR11## wherein R₉, R₁₀ and R₁₁ are each hydrogen, alkyl having 1 to 8 carbon atoms, halogen or phenyl and M is zinc, aluminum, magnesium or calcium.
 6. A method according to claim 5, wherein the amount of the gelation inhibitor is 0.001 to 5% by weight based on the liquid polymer.
 7. A method according to claim 6, wherein the amount of the gelation inhibitor is 0.005 to 0.5% by weight based on the liquid polymer.
 8. A method according to claim 5, wherein the addition reaction is carried out at 120° to 230° C for 1 to 10 hours.
 9. A method according to claim 8, wherein the reaction temperature is 170° to 210° C.
 10. A method according to claim 5, wherein the gelation inhibitor is a metal salt of a mercaptothiazole selected from the group consisting of the zinc salts, calcium salts, magnesium salts and aluminum salts of 2-mercaptothiazole, 2-mercapto-4-methylthiazole, 2-mercapto-5-methylthiazole, 2-mercapto-4,5-dimethylthiazole, 2-mercapto-4-ethylthiazole, 2-mercapto-4-chlorothiazole, 2-mercapto-4-phenylthiazole, 2-mercapto-4-methyl-5-phenylthiazole, 2-mercaptocyclohexenothiazole and 2-mercaptobenzthiazole. 